The present invention relates to a device for securing tips to rod-shaped articles such as cigarettes by wrapping the junction between a tip member and the body of a cigarette with a connecting sheet and adhesively bonding the inner face of the sheet to the body and to the tip member.
A device of this type usually has offered to it assemblies each consisting of a cigarette on each side of a tip member of double the usual length. In the device, the entire tip and the immediately adjacent region of each cigarette is wrapped with a connecting sheet, the longitudinal edges of which overlap each other, usually around a very short section of the circumference. After the joint has been made, the assembly is divided in the middle, after adhesive on the inner face of the sheet has hardened.
A number of known devices posses a grooved drum, upon the periphery of which grooves, suited to the shape of cigarettes, extend parallel to its axis. The assemblies or groups are pressed into these grooves, with the sheets beneath them, so that after a first step in the wrapping operation has taken place, the free ends of the sheets will have to be folded over from the two sides and pressed down.
One known machine for carrying out this second step is provided with a grooved drum in which radially movable flaps are incorporated. These flaps are lifted out under the control of camming means and are displaced so as to fold over the edges of the sheets from the two sides in succession under the action of stressed springs. Quite apart from the extraordinarily complicated construction of such a device, its principal disadvantage is that the flaps must immediately be moved in again. In a rapidly operating machine, the pressing time is not sufficient for the adhesive to harden, so that the joint can become loose again.
In another known machine, a second drum revolves in the same direction as and synchronously with a grooved drum, having upon its circumference closure members, intending for pressing one flap onto the group and for orienting the other sufficiently far for pressing on for a fixed pressing member, disposed after it in the direction of rotation, to be able completely to press on the still free flap. In this arrangement, the pressing-in of the first laid flap takes place only during a very short instant, and in this case also reliable adhesion is not possible where the machine operates rapidly.
Finally, a machine is known in which the connecting sheets initially lie asymetrically relative to the centre of the groove, when the group is pushed in. There therefore remains still one freely projecting flap, which is moreover longer than with the other solutions referred to. In this known device, the free flap remains bearing against the circumference of the grooved drum, until the partially wrapped group is ejected. At this position of the circumference, a closure drum equipped with a soft elastic facing, is mounted to rotate in the same direction at a higher peripheral speed than the grooved drum. Interaction between the group and the soft elastic facing of the closure drum causes the group to be over the rolled flaps, after which the group is ejected. The construction of this device is relatively simple, but the results which can be achieved are not satisfactory; on the one hand the wrappings are non-uniform, indeed even undulating, while on the other hand the period of pressing-in is still not adequate for complete hardening of the adhesive.
Here it should be remembered that two types of adhesive are used; firstly, conventional water-soluble glues, which are applied onto the sheets before they are processed, and on the other hand heat-activated adhesives, with which the sheet material is coated in the first place and which, just before the wrapping and adhesive bonding operation, must be activated by being heated. During the hardening operation therefore, pressure must be applied with the first type until the moisture has evaporated, and with the other type until the applied heat has been removed; in the latter case therefore, the device must act as a "heat-sink".